Tracking and completing phone calls

It seems to me that one of the most difficult activities to track is a phone call that I need to make.

Unlike most other tasks, the physical action of a phone call can be completed (I dialed the number), but the action itself is still incomplete if:
1. There was no answer or the line was busy.
2. The call was answered but it went to voice mail, and I left a message.
3. The call was answered but there was no voice mail and I left a message with someone.
4. The call was answered, the person wasn't in, but I didn't leave a message.
or
5. I spoke to the person but there's still something to be done that will require another phone call.

I have done something, but I haven't completed the task.

I can now do a few things:
1. Re-schedule the call in the future: in a few minutes, a few hours, or a few days.
2. Make a note of the outcome and make no other change to the task.
3. Check off the task as completed and create a new task for the follow-up call.
4. Create a subtask for the follow-up call and leave the Parent task unchecked.
5. Check off the task as complete and forget about it.

It's clear the best approach will depend on the outcome of the first phone call. I haven't formulated a clear of guidelines on how to handle incomplete phone calls.

Phone calls and emails are both tricky for me, and they are my 2 most important contexts (I honestly haven't been able to figure out many other contexts that are useful for me. I will tell you what I do with your first 1 through 5 above.
1) Do nothing, or make a quick entry in the notes field that I could not reach the person and when, then move on.
2) Make a note in the notes field that the message was left. If all the needed information was in the message, I set the task to deferred (it has been delegated to a machine), and wait to check it off until I know the message was recieved. If it was the sort of call that required feedback, a response, etc. I set the task to waiting as I am expecting a call back.
3) Same as 2 except note who the message was left with.
4) Same as 1 except the note would obviously be different if I decided to make one.
5) It kind of depends on the nature of the call, but generally I like to check off the old task, and make a new one.

If I did not complete the task based on any of the reasons Claudio mentioned. I simply enter a date in the notes area and the details of the call.

10/05/2009 - Left voice message. If I requested for the person to get back to me, I will change the task to my "Waiting for" list.

I do the same with emails.

10/05/2009 - Sent Joe an email about the data I need.

For this task, I will change it to my "Waiting for" list since I expect Joe to take the next action on my email. When I review my task during the week, I can always see the task there and send another email if Joe has not done anything.